The present invention relates in general to magnetic brush development apparatus for applying developer material to a latent image in an electrostatographic reproduction apparatus, and more particularly to a magnetic brush development apparatus including a device for improving the mixing of replenished pigmented marking particles and developer material.
Magnetic brush development apparatus for applying developer material to a latent image in an electrostatographic reproduction apparatus are well known in the art. Such apparatus may include a housing having a sump portion which contains a supply of developer material. When the developer material comprises a mixture of magnetic carrier particles and smaller pigmented marking particles, the material in the sump is agitated to triboelectrically charge the material prior to delivering it to a magnetic brush where it can be brought into association with, and transferred to, an electrostatic latent image to develop such image.
Copending, commonly assigned U.S. Pat. No. 4,887,132, issued Dec. 12, 1989 in the names of Joseph et al, and U.S. Pat. No. 4,671,207, issued June 9, 1987, in the name of Hilbert disclose magnetic brush development apparatus particularly suitable for use with developer material having pigmented marking particles and permanent magnetic carrier particles, such as disclosed in U.S. Pat. No. 4,546,060, issued Oct. 8, 1985, in the names of Miskinis et al. More particularly, the disclosed apparatus include a ribbon blender that is used for agitating (mixing), feeding and triboelectrically charging such material in the sump portion of a magnetic brush development apparatus, and a feed mechanism that delivers material from the sump portion to a magnetic brush. The ribbon blender is constructed to provide uniform flow distribution of developer material across the length of the apparatus so that a sufficient supply of material is delivered to the magnetic brush over its full extent to uniformly develop the entire latent electrostatic image. It has been found that under certain conditions the mixing of replenished pigmented marking particles and developer material does not completely occur. That is, the marking particles do not charge sufficiently to disperse and adhere to the carrier particles in the developer material in the sump of the development apparatus. This may result in the generation of unacceptable artifacts in the developed image.